Cross-layer performance analysis of joint rate and power adaptation schemes with multiple-user contention in Nakagami fading channels

Abstract

Adaptively adjusting transmission rate and power to concurrently enhance goodput and save energy is an important issue in the wireless local area network (WLAN). However, goodput enhancement and energy saving are two contradictory goals, since high data rate usually requires high transmission power to meet the bit-error-rate (BER) requirement. To achieve the tradeoff between energy efficiency and goodput, therefore, we suggest a fast channel-driven rate and power adaptation (CDRPA) algorithm. Furthermore, we develop a physical (PHY)/medium access control (MAC) cross-layer analytical method to evaluate goodput and energy efficiency, incorporating the impacts of Nakagami fading channel and the carrier sense multiple access (CSMA) MAC protocol. This paper compares two adaptation schemes. The power-first scheme first selects the transmission power and then the data rate, aiming at energy saving. On the contrary, the rate-first scheme first selects the data rate and then the transmission power, aiming to enhance goodput. Numerical results show that the power-first scheme achieves better energy efficiency. However, the rate-first CDRPA scheme can indeed boost goodput, while maintaining comparable energy efficiency as the power-first scheme.